The cardiopulmonary adjustments to pain, exercise and assumption of an upright posture are mediated by somatoautonomic reflexes (SAR's). The mechanisms and neurochemical substrates integrating SAR's are unresolved and require anatomical studies to lay the groundwork. This proposal seeks to establish the neuroanatomic basis for spinal and brainstem mechanisms integrating SAR's, in particular those involved in the reflex regulation of arterial blood pressure and central cardiopulmonary integration. The experimental design consists of 3 interrelated light and electron microscopic studies. Study I employs retrograde, anterograde and immunocytochemical techniques to establish intraspinal projections to sympathetic preganglionic and phrenic motor neurons, as identified neurochemically or by retrograde transport from sympathetic ganglia or adrenal medulla and phrenic nerve. Study II will establish: 1) synapses between spinal projections and reticular-, vestibular- or other spinal premotor neurons innervating the intermediolateral cell columns or phrenic motor nucleus; 2) their origins in cord; 3) whether spinal autonomic afferents derive from independent neurons or collaterals; and 4) their chemical mediators. Study III will define morphological substrates for the role of the cerebellum in SAR's. Combined tracer techniques will seek to: 1) define the anatomical projections of areas of fastigial nucleus and cerebellar cortex eliciting pressor or depressor responses (FPR or FDR), or known to release vasopressin and adrenal catecholamines; and finally 2) establish anatomical circuits integrating cerebellar-autonomic reflexes and autonomic projection neurons in spinal cord and vestibular complex.